The present invention relates to a code-operatable electronic lock attachment, in particular to a lock attachment for a standard mortise lock.
The term "attachment" as used herein is not meant to exclude the possibility of manufacturing a mortise lock of which the object of the invention is an integral part.
The acute security consciousness of a population having to cope with a rising crime rate and an increasingly sophisticated criminal element has amongst others produced a large industry dealing primarily with access control at all levels, from military installations to office buildings, and from five-star hotels to road-side motels to private homes.
The classical access-control means, the simple, but easily picked tumbler lock has long been abandoned in favor of the cylinder lock which, though still pickable by expert fingers, is much safer as long as the keys don't fall, even temporarily, into the wrong hands, because nothing is easier than to prepare a perfect copy of such a key. Larger establishments, especially hotels, have therefore started to periodically switch the cylinders of their locks, an expensive procedure if carried out frequently, and a useless one if performed too infrequently.
The next step was the discarding of the mechanical lock and its replacement by an electromagnetically operated one that could be controlled by an electronic circuit activatable by an encodable card plus the personal code of the user to be keyed into a push button unit. The card codes could be easily changed, thus facilitating invalidation of such cards whenever the situation warranted such a step. These locks and their peripherals are, however, very expensive, and their use is justified only in high-level security applications. A less expensive access-control method suitable for office buildings, hotels, and the like, was to retain the mechanical locks and to provide an electro-magnetically operated strike that, when activated by an electronic circuit enabled by a code-bearing card, would release the lock bolt. However, the modifications required, such as the introduction of the strike-operating solenoid, the mounting, on the door frame, of the electronic circuitry, including the card reader, etc. etc., demanded the skill of an expert and were therefore so expensive as to militate against wider use of this basically sound idea.